The present invention relates to eye protection devices for preventing eye injuries due to incident broadband, high intensity light, and more particularly to such a device which is normally transparent, yet which becomes opaque within a few nanoseconds when irradiated by high intensity light over a broad band of wavelengths.
Military applications of single wavelength and tunable wavelength lasers operating in the visible (400-700 nm) and near-infrared (700-1200 nm) spectral regions are increasing rapidly. Consequently, the protection of the eyesight of military personnel against high intensity laser light from hostile and friendly forces is a major concern. A desirable protective device would be a goggle with the following major features. First, the goggle should be transparent over a broad wavelength range, unless irradiated at a light intensity above the threshold for eye damage. Second, the goggle should block the incident light a few nanoseconds after being irradiated above the damage threshold. Third, the goggle should provide ballistic and chemical protection.
At present, there is no eye protection device against high intensity light sources which (1) is transparent over a broad wavelength range, unless irradiated at a light intensity above the threshold for eye damage, and (2) becomes opaque within a few nanoseconds for intensities exceeding the threshold intensity for a broad band of wavelengths.
Devices have been developed to protect against high intensity light like a nuclear flash. However, none of these device are both (1) transparent over a broad wavelength range below the eye damage threshold, and (20 become opaque within a few nanoseconds for intensities exceeding the threshold for a broadband of wavelengths. A table of developed or potential devices, their response times, and their capability to offer broadband protection is given below.
__________________________________________________________________________ Approximate Response Development Device Time (sec) Broadband Stage __________________________________________________________________________ Liquid crystal .about.10.sup.-3 Yes Developed. light value PLZT or other &gt;10.sup.-6 Yes Developed. ferro-electric electro-optic shutter Image converter &gt;10.sup.-6 Yes Developed. Awkward for a foot soldier. Holographic 10.sup.-12 -10.sup.9 No Developed. Diffraction Optics Photochromic &gt;10.sup.-8 Yes Potential. Difficult to simultaneously transmit and protect against visible light. Electrochromic &gt;10.sup.-9 Yes Potential. High Effect fields (10.sup.6 -10.sup.7) required. Semiconductor &gt;10.sup.-9 Yes (IR & Near Potential. Metal VO.sub.2 Light IR) (Visible) Valve Non-Linear &gt;10.sup.-12 &gt; 10.sup.-9 Yes Potential. Requires Optical much higher light Phenomena intensities than the damage threshold, or an awkward focussing assembly. __________________________________________________________________________
In summary, the developed broadband devices do not have fast enough response times. The proposed devices may be capable of fast response times, but have the indicated problems regarding their development.
It is therefore an object of the invention to provide an eye protection device which is transparent over a broad wavelength range until irradiated at a light intensity above the threshold for eye damage, and which becomes opaque within a few nanoseconds for incident light intensities exceeding the threshold intensity for a broad band of wavelengths.